my web 0.2 website

In between browsing Facebook and Youtube, the UK economy generates $1,930,000,000 of output a year. Thats $550,000 every two and a half hours. Well if today had been a work day, there’d have been one two and a half hour period where that was much higher. That’s because in a pique of routing excitement, Pakistan Telecom managed to hide Youtube from most of the internet for that length of time.

Pakistan Telecom and Youtube are likely to have no commercial relationship in place to carry Youtube traffic - particularly as around two hours ago, according to Yahoo News, the story broke that the Pakistan Government required ISPs operating in the country to block Youtube. Despite this, Pakistan Telecom were able to cause ISPs all over the world to send traffic that should be destined for Youtube to Pakistan instead.

This is because the protocol that determines how to find my network on the internet, is shaped by how “specific” the announcement of my network is. If I make an announcement of a network of 1,024 addresses, and someone else makes a second announcement of 256 addresses within a subset of my 1,024, then the network which announces the smaller subset win the traffic destined to those hosts. This is a feature - fully by design - of the BGP routing protocol. Almost every time a more specific block of addresses is announced, this is because the administrators of those networks intend for the routing to be different for a subset of a large number of addresses.

Sadly, there are accidents from time to time - another network can announce a subset of my addresses without my knowledge or permission, and they win the traffic that should have gone to me. This happened today - it seems that Pakistan Telecom decided to inject a fake route to their network containing Youtube’s webservers, and accidently then leaked that route to the networks they connect to.

Small networks and end sites can limit the chances that they will leak bad routes by explicitly listing the network addresses that they intend to send to their upstream or peered networks. Larger networks may find it harder to stop themselves propagating someone else’s mistake, because they may have a contract to carry forward any announcement that their customers make. Furthermore, the complexities of their own networks mean that an engineer working under pressure after announcements made by government ministers are more likely to make a typo error and do the wrong thing.

Richard Clayton presented a very interesting set of commentaries at the last LINX meeting. He commented that right now its very obvious indeed when someone hijacks some of my network space in this way, because all of my traffic disappears. Youtube were probably aware that something was very wrong within moments of the announcement. What if someone builds an infrastructure to steal my traffic - or at least some of my traffic - but after doing something with it, they send it back to me, it is much harder for me to spot that anything is wrong.

This is a significant risk to ecommerce infrastructures that competitors or e-pirates could seize upon opportunities to steal customer behaviour data. What if a wizard stole the network containing your web server, proxied your shop, but set up a fake checkout? How quickly would you spot?

Because this problem is inherent to the routing protocol, this is the obvious place to fix it. There are attempts to blend PKI with routing information, so that peers can verify the validity of your announcements. S/BGP (secure BGP) requires me to sign my announcements, and gives my peers a method to check in an impartial internet community database that my announcement is valid. It is the sort of technology that would have prevented Youtube from disappearing off the air today.